Steve Smith uncertain about Test future

Steve Smith has admitted he is unsure how much longer he will play Test cricket and is set to take a tour-by-tour approach to his future.

Australia is bracing for a changing of the guard in the coming years, with opening batters Usman Khawaja and David Warner both entering the twilight of their careers at 36 years of age and 33-year-old Smith not far behind.

Smith remains at the top of his game and scored 104 runs in the third Test against South Africa on day two at the SCG to climb into equal third place on the list of most Test centuries by an Australian.

Earlier in the summer, Smith doubted whether he had enough time left in his career to surpass Ricky Ponting's Australian record of 41 Test tons but at stumps on day two against the Proteas, he went one step further.

When asked, Smith said he could not guarantee how many home Test summers he would play in.

"We'll see. I'm enjoying it at the moment," Smith told reporters after Australia were 4-475 at stumps.

"I really can't say how long I'll play for. I'm not sure.

"I'll take it one tour at a time, just enjoy it, enjoy training and trying to get better as well. Whilst I'm doing that, I'm happy playing but I don't know how long that'll last."

Using his experience to assist his teammates remains a priority for Smith, especially as Australia braces for tough tours of India and England between now and next summer.

"For me, it's about trying to get better and try to help some of the other batters coming through," he said.

"Just try and impart as much knowledge of conditions and ways to go about it.

"If I can say something and see that lightbulb go on when someone figures something out, I get a big thrill out of that."

Records tumbled for Smith on Thursday; his latest century was his fourth at the SCG meaning he trails only Ponting (six) in tons scored at the famous ground.

The century also helped him become just the sixth man to have scored more than 1000 Test runs there.

With one more century, Smith will break clear of Matthew Hayden into outright third place on the list of hundreds scored by an Australian and will be only one ton behind second-placed Steve Waugh (32).

"I don't play for that kind of stuff but it was cool to look up and see my name amongst those great players," he said.

"It was pretty special."